To machine workpieces, for instance plate-like workpieces such as sheet metal, in laser machining systems, a workpiece rest is generally provided. The workpiece rest may, for example, include a frame with a plurality of rest elements which are arranged generally parallel to one another and on which the workpiece to be machined rests. The rest elements usually have supporting point peaks at regular intervals and form a rest field for the workpiece(s).
Laser machining systems of this type comprise a laser cutting head which is movable relative to the workpiece rest in order to machine a substantially stationary workpiece, which rests on the supporting point peaks of the rest elements, by means of a laser beam. During the machining, problems occur as the laser beam passes over the supporting point peaks, such as for example damage to the supporting point peaks as a result of welding deposits, damage to the supporting point peaks as a result of their being melted away, and/or a non-uniform cut between the product part and the residual part, since the cutting conditions at the supporting point peaks are different from those at the adjacent supporting point peaks.
In order to reduce the above-stated problems in the machining of the workpieces, DE 38 03 918 A1 describes a workpiece rest in which the rest elements can be lowered as a function of the position of the laser beam during the machining process. A mechanism which is coupled to the cutting head serves to lower in each case that rest element which is situated in the impingement region of the laser beam during the machining process.
A similar design is likewise known from JP 59127988 A. The rest strips are activated by means of a cam guide, with a lowering movement and a displacement movement in the longitudinal direction of the rest element being provided simultaneously.
In both of the above-described workpiece rests, a lowering of the supporting point peaks is effected over the entire length of the rest elements, reducing weld deposits on the supporting point peaks as they are traversed during the cutting process. However, non-uniform cuts may still occur, in particular when a workpiece is almost completely cut out from the workpiece table and rests with one end on the lowered supporting point peaks.
JP 2001-259878 A2 describes a laser machining system for producing electronic printed circuit boards, in which uniform bore diameters and bore shapes are required. A printed circuit board of this type rests, for machining, on a workpiece rest. In order that machining can take place in a manner not influenced by the workpiece rest, the workpiece rest has a series of parallel depressions which are arranged adjacent to one another and in which rest peaks are provided so as to be longitudinally movable. Said rest peaks are moved as a function of the machine data for producing the printed circuit boards, thereby making uninfluenced machining possible. However, during the machining process, burned-off portions, slag and dust which are deposited, and the chips which are generated during the production of bores, may contaminate or block the guides of the rest peaks, and can therefore result in the workpiece rest becoming non-operational. Handling tends to be impaired on account of the high cleaning expenditure. Furthermore, during the machining of printed circuit boards, there is not the problem that, after the machining process, a separate product part and residual part is present, with it being necessary for the product part and also the residual part to be reliably held by the rest elements until the complete unloading of the workpiece rest.